This invention relates to an intake system for a multi cylindered engine and more particularly to an improved induction system for an engine that includes a pair of plenum chambers and an improved arrangement for introducing atmospheric air to the plenum chambers.
In the induction system for an internal combustion engine it has been found that certain advantages can be achieved by employing a plenum chamber in the engine induction system. Such plenum chambers have the advantage of damping pulsations in the intake flow to the chambers of the engine and also facilitate tuning. With certain engines, there is a further advantage in employing a plurality of plenum chambers for the engine. For example, if the engine is provided with cylinders arranged in banks, either V type or opposed engines, there may be certain advantages in providing a separate plenum chamber for each cylinder bank of the engine. However, where plural plenum chambers are provided there is an advantage in incorporating a single intake for all of the plenum chambers. The use of such a single intake, permits a single air filter element, single air silencer and single flow controlling throttle valve. As a result, certain simplicities and cost reduction may be achieved. An example of an engine embodying such an induction system may be found in co-pending application Ser. No. 634,795, filed July 26, 1984 and now U.S. Pat. No. 4,649,876 in the name of Masatoshi Omi et al, entitled "Intake Means of Internal Combustion Engine" and assigned to the assignee of this application.
Although the system disclosed in the aforenoted co-pending application has been found to provided a number of advantages, it has recently been discovered that still further improvements in engine performance maybe achieved in connection with this type of induction system, That is, where the plenum chambers each have their inlets at one end of the chamber, it is found that there may be some restriction to the intake of the individual cylinders under certain running conditions. For example, under some running conditions the direction of air flow through the plenum chamber to an individual cylinder must reverse. That is, the middle cylinder of the plenum chamber may draw intake air from either end of the chamber under certain running conditions. As a result, there may occur reversals in air flow in the plenum chambers which can reduce volumetric efficiency. Further more, the use of the single air inlet for each plenum chamber may, itself, reduce the breathing capacity of the engine.
It is, therefore, a principle object of this invention to provide an improved induction system for an internal combustion engine.
It is a further object of this invention to provide an induction system for an internal combustion engine in which plural plenum chambers are employed and in which the performance may be improved even though the system is provided with a single air intake.
It is a further object of this invention to provide an improved induction system for an internal combustion engine embodying plural plenum chambers.
In the induction system disclosed in the forenoted co-pending application Ser. No. 634,795 each cylinder of the engine is provided with a pair of intake passages. One of these intake passages is served by the plenum chamber that is adjacent that cylinder bank while the other intake passage is served by the plenum chamber adjacent the opposite cylinder bank. In this way, the intake passages may be tuned to have different lengths and an improvement in performance throughout the entire engine load and speed ranges may be obtained. However, the disadvantages as aforenoted may be present in this type of induction system.
It is, therefore, a further object of this invention to provide an improved induction system for an engine having plural intake passages for each chamber of the engine.
It is a further object of this invention to provide an improved induction system for a multiple valve internal combustion engine.